The self-assessment deadline comes around at the same time every year, but thousands of people still miss it.

If you were required to submit a self-assessment tax return and did not file by 31 January, HM Revenue and Customs now treats the return as late. That does not mean the situation cannot be resolved, but it does mean penalties may already apply and further charges can build quickly if nothing is done.

Missing the self-assessment deadline does not mean the situation cannot be put right. But acting quickly can make a real difference to the penalties and stress involved.

The annual self-assessment filing deadline passed on 31 January. Anyone who was required to submit a tax return for the 2024 to 2025 tax year and has not yet done so will now be classed as late by HM Revenue and Customs.

An automatic penalty applies as soon as the deadline is missed, even if no tax is owed or the tax has already been paid.

What penalties apply now

The first penalty is a fixed £100 charge. This applies immediately once the deadline has passed and cannot usually be appealed unless there is a recognised reasonable excuse.

If the return remains outstanding for more than three months, further penalties can start to build up. These are charged at £10 per day, for up to 90 days, meaning an additional maximum penalty of £900.

If the return is still not filed after six months, HMRC may charge a further penalty. This is the higher of £300 or 5% of the tax due.

After 12 months, another penalty of the higher of £300 or 5% of the tax owed can be added.

Separate penalties apply if tax is paid late. These are charged at 5% of the unpaid tax after 30 days, six months and 12 months. Interest may also be added to any outstanding balance.

Even if you cannot pay in full, filing the return as soon as possible helps limit how far penalties can escalate.

Reasonable excuses and appeals

HMRC does allow penalties to be cancelled in limited circumstances where there is a reasonable excuse. These might include serious illness, a bereavement, or an unexpected event that genuinely prevented the return being submitted on time.

Being busy, forgetting the deadline, or not having all paperwork ready are not usually accepted as valid reasons.

Any appeal must be made after the return has been filed, not instead of filing it.

What to do if you cannot pay

If you have filed your return but cannot afford to pay the tax bill in full, you may be able to apply for a Time to Pay arrangement. This allows the tax owed to be spread over monthly instalments, subject to meeting HMRC’s criteria.

The option is usually available online for debts under £30,000, provided returns are up to date.

How we can help

If you have missed the deadline, the most important step is to deal with it promptly and correctly. We can help you file your outstanding return, check whether penalties are correct, and advise on whether an appeal is appropriate.

We can also liaise with HMRC on your behalf, help you apply for a Time to Pay arrangement, and ensure future deadlines are managed properly so this does not happen again.

If you would like support with a late return or ongoing self-assessment obligations, call us on 01904 787 973 or book a call with our team.